I started working on electronics at age 12 in 1969. During the 60s and 70s Zenith products, especially their televisions were clearly superior to others on the market.
Hey a video covering one of my Zenith tube radios. Awesome. I'll watch the whole vid when I have time. This is a big chassis for sure. Mine works well. I haven't been "under the hood" yet due to other projects, but this is certainly one I want to keep enjoying for decades to come. Thnx for covering this model. I'm not sure if mine is this exact model, but it looks to be the same radio. Can't wait to watch your "overhaul" of this classic!!
I have 2 of the Zenith wood table top radios with the electrostatic tweeter in them. They are not piezoelectric, they are a capacitor basically. I have heard they develop shorts, but mine have been tested with my Heathkit IT-28 capacitor leakage tester and did not have any leakage at high voltage levels. They are run right off of the audio output plate high impedance side of the audio output transformer. Maybe all it takes is for a spider to crawl inside and short it out, like a bug zapper!
One ☝️ of the best radios 📻 since sliced bread 🥖. Worked and worked and worked and worked is the best way to go. That tells ya that these radios 📻 weren’t junk. Odds are, this radio 📻 would probably still be working in the year 3022. I heard the news 🗞 on the broken 😞 dial cord. Ya may also wanna check the dial light 💡. Piezoelectric speakers 🔊 were often used in 1970’s and 1980’s electronics, but I never 👎 heard of them in the 1950’s, or 1960’s. They are a speaker 🔊 that work without a magnet 🧲. My idea 💡 was that they were more energy efficient than a field coil, or permanent magnet 🧲 speaker 🔊. Ya should call ☎️ that your Zenith truck 🛻. Your friend, Jeff.
Zenith model X338 . It has the 8H20 chassis ( but your intro says it's a C845M which has chassis 8C02). Same 8 tubes. Yours doesn't have a phono jack. That is the only difference! Zenith radios used mostly disc capacitors but there are always wax paper ones. I see a pale blue disc cap in there where the power comes in . Always replace thoses! They are usually bad ( open) or will fail shortly and this one is probably a 0.047uF. Cathode of a diode symbol has the line closest to it. That side goes to the electrolytics with a low value resistor before them. Usually there is a + mark on the Selenium rectifier.That should help you in case of any doubt, sometimes. Works like a champ as always and sound excellent.
Zenith made great radios. I bought one of their wooden table top radios a couple years ago that worked great with only its original electrolytic replaced sometime before I acquired it. It pulled in two stations that I had never heard of and when I looked up their call signs one was in Chicago and the other in Cincinnati which was impressive when I live in western Iowa and it was just sitting on the counter using only its internal antenna. I haven't used it more than a handful times to show it off to others because sadly I haven't had the time to recap and restore it.
I always love your videos. Could you move your fixed chassis view to the side of the chassis you’re working on? Electrolytic replacement would be so much clearer for viewing in smaller screens. Thanks!
I have a Admiral radio made a lot like this one I restored a couple years ago, It has a 6x9 Speaker and it sounds pretty good, Even after the Resto FM seems to not have the best selectivity, Jordan Pier told me it could be Silver Mica disease :(
Cathode, think of cats, i dont like cats so much so cats are negative. You changed the resistor to a power resistor, just wanted to know how you picked the ohms needed. I have several old console stereo systems with selenium rectifiers and want to change those out and would like replace with a diode. Does the quick rise in voltage with the solid state diode cause harm to the tubes when you convert?
I just generically use 50 ohm resistors for most AA5 type sets. As far as solid states ones? Who knows since obviously those use a lot less voltage. There is definitely some math that you can apply. I'm sort of dumb when it comes to actual math but I'm sure that can be found somewhere....www.antiqueradios.com/forums/viewtopic.php?f=3&t=260172
Seriously, about the cats... O.K., to your questions then: You can see that Zenith wasn't worried about an abrupt turn-on of the HT ("High Tension". "Voltage", they call it in the colonies🧐) because a selenium rectifier is also "solid-state" in its behaviour as a rectifier. It's "ON" resistance is somewhat greater than that of a silicon diode, but in practice all that means is a lower voltage under load. The charge-up time of that 80-40-40-40μF capacitor in the radio will be all but identical whether a silicon, germanium, or selenium rectifier is used. And since there is no load on the power supply once the rectifier has fully charged that filter capacitor, and many more seconds will pass until such time as the filaments in the valves(tubes) wake up, slowly slowly. It takes 15-20sec. for the last valve to be operating fully. Since Zenith was using an "instant on" rectifier to start with, they have clearly designed in the headroom, the additional surge voltage rating, into the capacitor that was used originally. So that takes your worry away from capacitor overvoltage stress that's more likely to occur if you were replacing a TUBE rectifier with a SOLID-STATE rectifier! Your next question should now answer itself. But I think it's an extremely good one, & very thoughtful of you to consider it. Zenith clearly had no fear of exposing the valves(tubes) in their sets, ones with THEIR Brand Name & THEIR WARRANTY on them, to 15 seconds or less of high voltage hovering over their still-cold cathodes, every time you turned the set on. Nor did they worry about an insufficiently heated cathode being "stressed" by running flat out momentarily until it heated up enough to keep up with the Anode(Plate) "pull", or "demand" or whatever else you might think is messing with the cathode's chemistry under "unusual" conditions of operation. Myth #1: Applying High Tension to a cold valve can strip the cathode coating due to excessive & persistent high intensity electrostatic field. Sure it can. IF it's a cathode ray tube, typically. Where there aren't a few HUNDRED volts being applied. There are several THOUSAND volts being applied. And there isn't, to my knowledge & experience, any effect at much lower voltage if the period of time the exposure occurs is even INFINITELY long! I know, because I've built my own audio gear & that's how I've been operating it for DECADES now (so going into my 40th year of doing this to fragile things like 12AX7's & 6DJ8's & 6SN7's. Absolutely NO effect, neither bad nor good. But charging the electrolytics continuously improved their performance & longevity substantially! Myth #2 Is it safe to START warming up a valve filament in the presence of the full rated High Voltage? Shouldn't the filament & cathode be up to absolutely full operating temperature for optimum emission potential BEFORE high voltages are applied? Sure, if the tube we're talking about is a giant cauldron of mercury called an Ignitron, which is (was...) designed to handle 10's if not 100's of thousands of amperes of current flowing through them! Also there are smaller mercury-vapour rectifiers that were popular in Ham Radio use in the transmitter power supply, especially if it was well over 100 watts output. Those rectifiers like the 816 & 866/A were used when you needed at least 1500V on your output valves, I've seen home-brew Ham transmitters that ran from 4000V "Plate" supplies. So yes, there are certain weird & distinctly never going to be used anywhere near Audio vacuum tubes that need to be treated with special handling. But since home audio equipment only uses valves with a hard vacuum in them, obviously including any table radio ever made that you can think of, we're safe treating them without concern for whether the High Tension or full filament warmup are applied first. I've handled thousands upon thousands of valves in my life (& now another 8 in this Zenith🤗), & have NEVER seen a valve experience any cathode emission failures that could be attributed to doing this "wrong". So sleep well, relax. There IS no "wrong way". Postscript: If you're going to worry about anything that's especially detrimental to valve life, it's maintaining the heater voltage as absolutely close to its nominal rating as possible. Operation for prolonged periods with the filament & cathode running at outside their nominal temperatures, whether it be too low or too high, will vastly decrease the service life of the cathode (& therefore, the rest of the bloody thing🧐). Too low doesn't extend valve life; it poisons the cathode chemistry alot faster. Too high also cuts valve life short: excess emission also poisons/exhausts the cathode chemistry prematurely. It also causes the valve to be subject to temperature stresses that can cause filament to cathode shorts, & worse; especially if the excess filament voltage is partnered with full-on Class A operation. Like say, a "tube" table radio.😘
Mister Radio hooked me up with one two years ago. It's my daily driver, still sounds and works great. Thanks Seth!
Seth your Truck is lovely and the fact you have had it from new makes it even more precious and unique.
Its basically like an old friend. Hilarious to think I've had it for a lot longer than I've been married to my wife.
@@misterradio5035 and you have taken great care of it too.
I still remember Zenith's slogan: " The quality goes in before the name goes on."
I started working on electronics at age 12 in 1969. During the 60s and 70s Zenith products, especially their televisions were clearly superior to others on the market.
Hey a video covering one of my Zenith tube radios. Awesome. I'll watch the whole vid when I have time. This is a big chassis for sure. Mine works well. I haven't been "under the hood" yet due to other projects, but this is certainly one I want to keep enjoying for decades to come. Thnx for covering this model. I'm not sure if mine is this exact model, but it looks to be the same radio. Can't wait to watch your "overhaul" of this classic!!
Beautiful finish on that one Seth..Great fix and info...So interesting as always..Ed..uk..😀
I have 2 of the Zenith wood table top radios with the electrostatic tweeter in them. They are not piezoelectric, they are a capacitor basically. I have heard they develop shorts, but mine have been tested with my Heathkit IT-28 capacitor leakage tester and did not have any leakage at high voltage levels. They are run right off of the audio output plate high impedance side of the audio output transformer. Maybe all it takes is for a spider to crawl inside and short it out, like a bug zapper!
Mrster radio the zenith c 845 high fidelity radio Receiver is so awesome
I just bought this exact model at a local estate sale for $20. Works great. Picks up EVERY FM station.
Zenith daily driver! Those are so good!
One ☝️ of the best radios 📻 since sliced bread 🥖. Worked and worked and worked and worked is the best way to go. That tells ya that these radios 📻 weren’t junk. Odds are, this radio 📻 would probably still be working in the year 3022. I heard the news 🗞 on the broken 😞 dial cord. Ya may also wanna check the dial light 💡. Piezoelectric speakers 🔊 were often used in 1970’s and 1980’s electronics, but I never 👎 heard of them in the 1950’s, or 1960’s. They are a speaker 🔊 that work without a magnet 🧲. My idea 💡 was that they were more energy efficient than a field coil, or permanent magnet 🧲 speaker 🔊. Ya should call ☎️ that your Zenith truck 🛻. Your friend, Jeff.
Must be a very sensitive receiver, seems to have 3 if stages. Thanks for the video.
I've got my dad's radio. Still works and sounds great with original tubes.
Zenith model X338 . It has the 8H20 chassis ( but your intro says it's a C845M which has chassis 8C02). Same 8 tubes.
Yours doesn't have a phono jack. That is the only difference! Zenith radios used mostly disc capacitors but there are
always wax paper ones. I see a pale blue disc cap in there where the power comes in . Always replace thoses! They are
usually bad ( open) or will fail shortly and this one is probably a 0.047uF. Cathode of a diode symbol has the line closest
to it. That side goes to the electrolytics with a low value resistor before them. Usually there is a + mark on the Selenium rectifier.That should help you in case of any doubt, sometimes. Works like a champ as always and sound excellent.
Hi, I bought two of these today. I have not checked them out yet.
Zenith made great radios. I bought one of their wooden table top radios a couple years ago that worked great with only its original electrolytic replaced sometime before I acquired it. It pulled in two stations that I had never heard of and when I looked up their call signs one was in Chicago and the other in Cincinnati which was impressive when I live in western Iowa and it was just sitting on the counter using only its internal antenna. I haven't used it more than a handful times to show it off to others because sadly I haven't had the time to recap and restore it.
I always love your videos.
Could you move your fixed chassis view to the side of the chassis you’re working on? Electrolytic replacement would be so much clearer for viewing in smaller screens. Thanks!
What are the specs on the isolation transformer (wall wart) that you install for MP3 playing? Where do you find them? Amazon? Thanks!
Isn't it GLORIOUS when you get to answer your own question?😜
Congratulations to you "Uncle" Seth.
😊 Zenith Radio and TV 📺 Stereo was the very best 👌 👍 😊, nothing made that good anymore !!
These are good radios. I have 3 of them--they're the poor man's KLH 20.
The rich man can keep his!😘🤗😉
I have a Admiral radio made a lot like this one I restored a couple years ago, It has a 6x9 Speaker and it sounds pretty good, Even after the Resto FM seems to not have the best selectivity, Jordan Pier told me it could be Silver Mica disease :(
.mrster radio that is cool when you put in the jack in the radio so you can play your cellphone
Cathode, think of cats, i dont like cats so much so cats are negative.
You changed the resistor to a power resistor, just wanted to know how you picked the ohms needed. I have several old console stereo systems with selenium rectifiers and want to change those out and would like replace with a diode. Does the quick rise in voltage with the solid state diode cause harm to the tubes when you convert?
I just generically use 50 ohm resistors for most AA5 type sets. As far as solid states ones? Who knows since obviously those use a lot less voltage. There is definitely some math that you can apply. I'm sort of dumb when it comes to actual math but I'm sure that can be found somewhere....www.antiqueradios.com/forums/viewtopic.php?f=3&t=260172
I'm reporting you to the EIA! For cruelty of something...some kind...🤔
😸
Seriously, about the cats...
O.K., to your questions then:
You can see that Zenith wasn't worried about an abrupt turn-on of the HT ("High Tension". "Voltage", they call it in the colonies🧐) because a selenium rectifier is also "solid-state" in its behaviour as a rectifier. It's "ON" resistance is somewhat greater than that of a silicon diode, but in practice all that means is a lower voltage under load. The charge-up time of that 80-40-40-40μF capacitor in the radio will be all but identical whether a silicon, germanium, or selenium rectifier is used.
And since there is no load on the power supply once the rectifier has fully charged that filter capacitor, and many more seconds will pass until such time as the filaments in the valves(tubes) wake up, slowly slowly. It takes 15-20sec. for the last valve to be operating fully. Since Zenith was using an "instant on" rectifier to start with, they have clearly designed in the headroom, the additional surge voltage rating, into the capacitor that was used originally. So that takes your worry away from capacitor overvoltage stress that's more likely to occur if you were replacing a TUBE rectifier with a SOLID-STATE rectifier!
Your next question should now answer itself. But I think it's an extremely good one, & very thoughtful of you to consider it.
Zenith clearly had no fear of exposing the valves(tubes) in their sets, ones with THEIR Brand Name & THEIR WARRANTY on them, to 15 seconds or less of high voltage hovering over their still-cold cathodes, every time you turned the set on. Nor did they worry about an insufficiently heated cathode being "stressed" by running flat out momentarily until it heated up enough to keep up with the Anode(Plate) "pull", or "demand" or whatever else you might think is messing with the cathode's chemistry under "unusual" conditions of operation.
Myth #1: Applying High Tension to a cold valve can strip the cathode coating due to excessive & persistent high intensity electrostatic field. Sure it can. IF it's a cathode ray tube, typically. Where there aren't a few HUNDRED volts being applied. There are several THOUSAND volts being applied. And there isn't, to my knowledge & experience, any effect at much lower voltage if the period of time the exposure occurs is even INFINITELY long! I know, because I've built my own audio gear & that's how I've been operating it for DECADES now (so going into my 40th year of doing this to fragile things like 12AX7's & 6DJ8's & 6SN7's. Absolutely NO effect, neither bad nor good. But charging the electrolytics continuously improved their performance & longevity substantially!
Myth #2 Is it safe to START warming up a valve filament in the presence of the full rated High Voltage? Shouldn't the filament & cathode be up to absolutely full operating temperature for optimum emission potential BEFORE high voltages are applied?
Sure, if the tube we're talking about is a giant cauldron of mercury called an Ignitron, which is (was...) designed to handle 10's if not 100's of thousands of amperes of current flowing through them! Also there are smaller mercury-vapour rectifiers that were popular in Ham Radio use in the transmitter power supply, especially if it was well over 100 watts output. Those rectifiers like the 816 & 866/A were used when you needed at least 1500V on your output valves, I've seen home-brew Ham transmitters that ran from 4000V "Plate" supplies.
So yes, there are certain weird & distinctly never going to be used anywhere near Audio vacuum tubes that need to be treated with special handling.
But since home audio equipment only uses valves with a hard vacuum in them, obviously including any table radio ever made that you can think of, we're safe treating them without concern for whether the High Tension or full filament warmup are applied first. I've handled thousands upon thousands of valves in my life (& now another 8 in this Zenith🤗), & have NEVER seen a valve experience any cathode emission failures that could be attributed to doing this "wrong".
So sleep well, relax. There IS no "wrong way".
Postscript: If you're going to worry about anything that's especially detrimental to valve life, it's maintaining the heater voltage as absolutely close to its nominal rating as possible. Operation for prolonged periods with the filament & cathode running at outside their nominal temperatures, whether it be too low or too high, will vastly decrease the service life of the cathode (& therefore, the rest of the bloody thing🧐).
Too low doesn't extend valve life; it poisons the cathode chemistry alot faster.
Too high also cuts valve life short: excess emission also poisons/exhausts the cathode chemistry prematurely. It also causes the valve to be subject to temperature stresses that can cause filament to cathode shorts, & worse; especially if the excess filament voltage is partnered with full-on Class A operation. Like say, a "tube" table radio.😘
Toyota is the Zenith of motor vehicles, that truck is a 500,000 mile vehicle with good care.
New Zealand in
you wouldnt bee driving that truck anymore here in wisconsin......the frame would of rusted in half 10 years ago.